Small performance tweaks to mirror status JSON encoding

Do a few things to speed up the encoding of the JSON, including better
usage of list comprehensions, less dynamic setattr() usage, and removal
of the queryset specialization since we can easily do it outside of the
encoder.

Signed-off-by: Dan McGee <dan@archlinux.org>

mirrors/utils.py

@@ -84,19 +84,16 @@ def status_data(cutoff=DEFAULT_CUTOFF, mirror_id=None):
 def annotate_url(url, url_data):
     '''Given a MirrorURL object, add a few more attributes to it regarding
     status, including completion_pct, delay, and score.'''
-    known_attrs = (
-        ('success_count', 0),
-        ('check_count', 0),
-        ('completion_pct', None),
-        ('duration_avg', None),
-        ('duration_stddev', None),
-        ('last_check', None),
-        ('last_sync', None),
-        ('delay', None),
-        ('score', None),
-    )
-    for k, v in known_attrs:
-        setattr(url, k, v)
+    # set up some sane default values in case we are missing anything
+    url.success_count = 0
+    url.check_count = 0
+    url.completion_pct = None
+    url.duration_avg = None
+    url.duration_stddev = None
+    url.last_check = None
+    url.last_sync = None
+    url.delay = None
+    url.score = None
     for k, v in url_data.items():
         if k not in ('url_id', 'mirror_id'):
             setattr(url, k, v)
@@ -107,7 +104,7 @@ def annotate_url(url, url_data):
     if url.delay is not None:
         hours = url.delay.days * 24.0 + url.delay.seconds / 3600.0
 
-        if url.completion_pct > 0:
+        if url.completion_pct > 0.0:
             divisor = url.completion_pct
         else:
             # arbitrary small value
@@ -115,6 +112,8 @@ def annotate_url(url, url_data):
         stddev = url.duration_stddev or 0.0
         url.score = (hours + url.duration_avg + stddev) / divisor
 
+    return url
+
 
 def get_mirror_statuses(cutoff=DEFAULT_CUTOFF, mirror_id=None, show_all=False):
     cutoff_time = now() - cutoff
@@ -133,8 +132,7 @@ def get_mirror_statuses(cutoff=DEFAULT_CUTOFF, mirror_id=None, show_all=False):
             id__in=valid_urls).order_by('mirror__id', 'url')
 
     if urls:
-        for url in urls:
-            annotate_url(url, url_data.get(url.id, {}))
+        urls = [annotate_url(url, url_data.get(url.id, {})) for url in urls]
         last_check = max([u.last_check for u in urls if u.last_check])
         num_checks = max([u.check_count for u in urls])
         check_info = MirrorLog.objects.filter(check_time__gte=cutoff_time)

mirrors/views.py

@@ -275,9 +275,6 @@ def default(self, obj):
         if isinstance(obj, timedelta):
             # always returned as integer seconds
             return obj.days * 24 * 3600 + obj.seconds
-        if hasattr(obj, '__iter__'):
-            # mainly for queryset serialization
-            return list(obj)
         if isinstance(obj, MirrorUrl):
             data = {attr: getattr(obj, attr) for attr in self.url_attributes}
             country = obj.country
@@ -298,8 +295,8 @@ def default(self, obj):
         if isinstance(obj, MirrorUrl):
             data = super(ExtendedMirrorStatusJSONEncoder, self).default(obj)
             cutoff = now() - DEFAULT_CUTOFF
-            data['logs'] = obj.logs.filter(
-                    check_time__gte=cutoff).order_by('check_time')
+            data['logs'] = list(obj.logs.filter(
+                    check_time__gte=cutoff).order_by('check_time'))
             return data
         if isinstance(obj, MirrorLog):
             return {attr: getattr(obj, attr) for attr in self.log_attributes}